02 Information System Security
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Information System Security 02 -general_applications_of_cryptography
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02 Information System Security
- 1. UCCN 1213 Chapter 2 General Applications of Cryptography October 2011
- 11. Examples A B C D E F G H I J K L M N O P Q R S T U V W X Y Z U T A R M Y C H O I E B D F G J K L N P Q S V W X Z i l o v e u = O B G S M Q l a z y = B U Z X c r y p t o = C L X J P G w o r m = V G L D k i l l r o s l a n = E O B B L G N B U F
- 16. Example
- 22. Weakness of Hill Cipher
- 31. Triple DES
- 52. Inverse of 5 in Z 17 Q A1 A2 A3 B1 B2 B3 — 1 0 17 0 1 5 3 0 1 5 1 – 3 2 2 1 – 3 2 – 2 7 1
- 64. Diffie-Hellman Key Exchange Protocol 11/22/11 Data Integrity
- 66. Public domain image from http://en.wikipedia.org/wiki/File:DiffieHellman.png
- 75. Data Integrity: Applications of Cryptographic Hash Functions
Notes de l'éditeur
- Cryptography and Encryption-Based Solutions Although not a specific application or security tool, encryption represents a sophisticated approach to security that is implemented in many security systems. In fact, many security-related tools use embedded encryption technologies to protect sensitive information handled by the application. Encryption is the process of converting an original message into a form that is unreadable by unauthorized individuals, that is, anyone without the tools to convert the encrypted message back to its original format. The science of encryption, known as cryptology, encompasses cryptography, from the Greek words kryptos, meaning hidden; graphein, meaning to write; and cryptanalysis, the process of obtaining the original message (or plaintext) from an encrypted message (or ciphertext), without the knowledge of the algorithms and keys used to perform the encryption.
- Cryptography and Encryption-Based Solutions The notation used to describe the encryption process differs depending on the source. The first uses the letters M to represent the original message, C to represent the ending ciphertext, and E to represent the encryption process: E(M) = C. This formula represents the application of encryption to a message to create ciphertext. D represents the decryption or deciphering process, thus D[E(M)]=M. K is used to represent the key, thus E(M, K) = C, or encrypting the message with the key results in the ciphertext. Now look at a simple form of encryption based on two concepts: the block cipher and the exclusive OR operation. With the block cipher method, the message is divided into blocks, i.e., 8- or 16-bit blocks, and then each block is transformed using the algorithm and key. The exclusive OR operation (XOR) is a function of Boolean algebra whereby two bits are compared, and if the two bits are identical, the result is a binary 0. If the two bits are NOT the same, the result is a binary 1.